With advance of metal organic chemical vapor deposition or molecular beam growth of gallium nitride (GaN), red, green and blue light emitting diodes (LEDs) capable of realizing high brightness and white light have been developed.
Such LEDs do not contain environmentally harmful materials, such as mercury, used in existing lighting equipment, such as glow lamps and fluorescent lamps and thus exhibits excellent environmentally friendly property, long lifespan and low power consumption. For this reason, the LEDs are replacing existing light sources. A core competition factor of such LED devices is realization of high brightness based on high-efficiency and high-power chip and packaging technology.